Solid electrolyte batteries are constructed using a solid-state electrolyte in the manner of a fuel cell. The electrolyte is arranged between two electrodes, of which one is an air electrode having a material which dissociates atmospheric oxygen and conducts the oxygen ions formed to the electrolyte. The electrolyte is likewise made of a material which can conduct oxygen ions. At the side of the electrolyte opposite the air electrode, there is the second electrode which includes a metal or metal oxide to be oxidized and reduced, respectively. The battery is discharged by the metal being oxidized by means of oxygen ions from the atmospheric oxygen and charged by the metal oxide being reduced with release of oxygen ions on application of a voltage, with the oxygen ions then migrating through the electrolyte to the air electrode from where they are released as molecular oxygen into the surroundings. Modern developments in the field of solid electrolyte batteries have led to the second electrode no longer being itself utilized as storage medium but an additional storage medium which is formed by the redox pair of a first metal and metal oxide being provided. An additional fluidic redox pair which transports the oxygen ions between the second electrode and the storage medium is then provided. The battery is operated at relatively high temperatures of up to 900° C.
The design of the storage elements hitherto starts out from a skeleton-like structure having a high open porosity. To reduce the tendency for sintering to occur at the operating temperatures prevailing in the solid electrolyte batteries, use is made of ODS (oxide dispersion strengthened) metal and metal oxide particles. Furthermore, the metal and metal oxide particles are separated from one another by a ceramic matrix.
During the discharging process, i.e. in the course of the oxidation process, oxygen ions diffuse into the metal particles of the storage element. Furthermore, diffusion of the metal atoms to the oxygen source of the battery also takes place during the oxidation process. This is a disadvantage in terms of the structural stability of the storage medium. To ensure very complete utilization of the storage capacity together with optimal charging and discharging kinetics, it is particularly important that the metal particles are very finely dispersed, i.e. with a large active surface area at which the oxidation and reduction processes can take place, in the storage element. However, as a result of the tendency of the metal to diffuse in the direction of the oxygen ion gradient, demixing of the storage structure and thus an increase in the interparticle contacts between the metal and metal oxide particles takes place in the medium term. This increase in the interparticle contacts leads, owing to the high operating temperature, to sintering of the particles and thus to a decrease in the active surface area of the metal particles present. This hinders the charging and discharging process and impairs the respective kinetics. In addition, the effectively utilizable storage capacity of the store is reduced thereby.